1. Technical Field of the Invention
The present invention relates to the administration of at least one extract of at least one plant of the Ericacea family, or composition comprised thereof, for preventively and/or curatively treating the signs of aging of the skin.
This invention especially relates to the administration of such extracts or compositions to inhibit the degradation of the skin and/or mucous membranes by inhibiting collagenases. Too, the present invention relates to a cosmetic regime/regimen for combating aging of the skin and/or mucous membranes.
2. Description of the Prior Art
Human skin consists of two layers or compartments, namely, a surface layer or compartment, the epidermis, and a deep compartment, the dermis.
Natural human epidermis is principally composed of three types of cells: keratinocytes, which form the great majority, melanocytes and Langerhans cells. Each of these cell types contributes, by virtue of its intrinsic functions, towards the essential role played in the body by the skin.
The dermis imparts to the epidermis a solid support. It is also the nourishing factor of the epidermis. It consists mainly of fibroblasts and of an extracellular matrix which is itself composed mainly of collagen, elastin and a substance known as ground substance, these components being synthesized by the fibroblasts. Leukocytes, mastocytes and tissue macrophages are also present therein. It also contains blood vessels and nerve fibers. In normal skin, namely, non-pathological and unscarred skin, the fibroblasts are in the quiescent state, i.e., non-proliferative, metabolically relatively inactive, and immobile.
These collagen fibers provide the dermis with its firmness. Collagen fibers consist of fibrils sealed together, thus forming more than 10 different types of structures. The firmness of the dermis is principally due to the entanglement of the collagen fibers packed together in all directions. The collagen fibers contribute to the elasticity and tonicity of the skin and/or mucous membranes.
The collagen fibers are under constant renewal, but this renewal decreases with age, leading to thinning of the dermis. This thinning of the dermis is also due to pathological causes such as, for example, the hypersecretion of corticoid hormones, certain pathologies or vitamin deficiencies (which is the case for vitamin C in scurvy). It is also accepted that extrinsic factors such as ultraviolet rays, tobacco or certain treatments (glucocorticoids, vitamin D and derivatives, for example) also have an effect on the skin and its collagen content.
However, various factors result in the degradation of collagen, with all of the consequences which may be envisaged on the structure and/or firmness of the skin and/or mucous membranes.
Albeit very strong, collagen fibers are sensitive to certain enzymes known as collagenases. A degradation of collagen fibers promotes the development of flaccid and wrinkled skin, which individuals, preferring the appearance of smooth and taut skin, have universally sought to combat.
Collagenases are part of a family of enzymes designated metalloproteases (MMPs) which are themselves members of a family of proteolytic enzymes (endoproteases) which contain a zinc atom coordinated to 3 cysteine residues and one methionine residue at their active site and which degrade the macromolecular components of the extracellular matrix and of the basal layers at neutral pH (collagen, elastin, etc.). These enzymes, which are very widespread in nature, are present, but poorly expressed in normal physiological phenomena such as the growth of organs and the renewal of tissues.
However, their overexpression in man and their activation are linked to many processes, sometimes pathological, which involve the destruction and remodelling of the matrix. This results in either an uncontrolled resorption of extracellular matrix or, conversely, the installation of a state of fibrosis.
The metalloprotease family consists of several well-defined groups based on their resemblances in terms of structure and substrate specificity (see Woessner J. F., Faseb Journal, vol. 5, 2145 (1991)). Among these groups, exemplary are the collagenases for degrading fibrillar collagens (MMP-1 or interstitial collagenase, MMP-8 or neutrophil collagenase and MMP-13 or collagenase 3), gelatinases which degrade type IV collagen or any form of denatured collagen (MMP-2 or gelatinase A (72 kDa), MMP-9 or gelatinase B (92 kDa), stromelysins (MMP-3) whose broad spectrum of activity addresses the proteins of the extracellular matrix such as glycoproteins (fibronectin, laminin), proteoglycans, etc., or, alternatively, membrane metalloproteases.
Prolonged exposure to ultraviolet radiation, particularly to ultraviolet rays of A and/or B type, has the effect of stimulating the expression of collagenases, particularly of MMP-1. This is one of the components of photoinduced aging of the skin.
Moreover, at menopause the principal changes concerning the dermis are a decrease in collagen content and in the thickness of the dermis. In menopausal women, this results in thinning of the skin and/or mucous membranes. Women then experience a sensation of “dry skin” or of taut skin and there is an increase in surface wrinkles and fine lines. The skin presents a rough aspect when touched. Finally, the skin is less supple.
The importance of collagen in the structure of tissues, particularly the skin and/or mucous membranes, and the importance of combating its degradation in order thus to combat aging, whether chronobiological or photoinduced aging and the consequences thereof, the thinning of the dermis and/or the degradation of collagen fibers which result in the development of flaccid and wrinkled skin, may thus be appreciated from the hereinabove description.